Gas detecting sensors have many applications. One such application is to detect the presence of a dangerous gas, or to detect a gas whose presence indicates a dangerous situation. For example, NASA (National Aeronautics and Space Association) has sponsored research in detecting low concentrations of sulfur dioxide (SO2) in closed environments, such as for example aboard the international space station or the space shuttle. SO2 could be a probable breakdown product from leaking lithium-thionyl chloride batteries. SO2 is a colorless gas or liquid under pressure with a pungent odor. Inhalation or exposure could have adverse effects on human health.
In addition to detecting various gases, or liquids, of interest, it may also be of utility to provide estimates of the concentrations of various gases or liquids of interest. For example, various industrial processes may require that various gases or liquids be present within some range of concentration levels. In other applications, some dangerous gases may be tolerated if their concentrations fall below some threshold level.